The use of sheet metal handles made from flexibly resilient, medical grade material has been pioneered by the present inventors beginning notably with U.S. Pat. No. 4,527,331 which addressed the problem of how to create a low cost, high quality scissors that opened automatically after closure. This development was followed by U.S. Pat. No. 6,592,603 which incorporated interlocking springs joining the ends of each pair of handles which significantly reduced the pressure needed to close the paired handles. The reduced force needed to close the handles enabled use of this design for development of several different manually-operated surgical instruments. Thereafter, U.S. Pat. No. 7,497,867 B2 taught mechanical changes which improved the stiffness and beam strength needed to achieve the desired resultant closing forces of the instruments. Surgical instruments that had stiffer and lower profiles broadened the applicability for this flexibly resilient sheet metal design, especially when the instruments were being used in tightly confined spaces frequently encountered during common surgical procedures.
U.S. Pat. No. 7,497,867 B2 taught use of the inventive handles as part of the design for manually adjustable scissors and forceps. However, needle holders using this design, while satisfactory for suturing mucosa or blood vessels, were inadequate at maintaining a secure hold on larger needles when pushed into denser tissue. The comparatively greater compressive force required to penetrate heavier and denser tissue results in undesirable flexion in weaker parts of the instrument which introduces instability during the suturing procedure. Furthermore, smooth surfaces on the outside of the sheet metal handles make them more prone to slip in the gloved hands of the surgeon when large manual forces are applied especially when the instrument handles become slippery in an environment prone to become wet. There exists, therefore, a current need for further improvements in flexible sheet metal handles for surgical instruments.
It is of course a requirement that a surgeon be able to maintain a firm, positive grip on an instrument during manual surgical procedures. Instabilities introduced by undesirable flexion or slippage of the tool must be avoided or mitigated. Many conventional surgical instruments—unlike the relatively flexible sheet metal instruments of the present invention—are machined from thicker, solid materials. These instruments are much heavier and less comfortable for the surgeon to use over long periods which results in greater strain and tiredness of the fingers, hands and arms. To make these heavier instruments easier to grip, cross-hatched knurling is often machined onto the outer surfaces of the handles. Instruments of the present design are not easily knurled as they are made from relatively thin, flat sheet materials. Knurling—a low height marking procedure—is not particularly effective when the surgical instrument being manipulated is lightweight which is one of the primary benefits of the sheet metal band design.
Another significant disadvantage of more conventional surgical instruments made from thicker solid materials—needle holders in particular—is that they are prone to permanent deformation if a needle too large in diameter is clamped in the jaws of the instrument, a not uncommon occurrence. Surgical needles generally have round cross sections and are not designed to be diametrically deformable. When a needle just slightly too large in diameter is forcibly clamped by the surgeon clinician using a conventional needle holder, the elastic limit associated with the jaw material of the scissor-like device is often exceeded permanently deforming the instrument by splaying the jaws out of tolerance. Therefore, an object of the present invention is to provide a sheet metal needle holder strong enough to resist excessive bending of the handle and yet flexibly springy and resilient enough to allow the jaw portion of a needle holder to accept a variety of different diameter needles without destroying the instrument.
An approach to one of the foregoing problems, taught by Bender in publication US20130247333 A1, describes the addition of protrusions extending radially outward from the sheet metal handle of a needle holder along its longitudinal axis. The idea is that the protrusions increase frictional engagement with the clinician surgeon's fingers compared to the more slippery condition presented by a smooth surface.
The instruments shown in the Bender application are known as Castroviejo and Barraquer microsurgical instruments. The needle holder, in particular, is intended to be used by a clinician who will hold or grip the instrument between thumb and fingers and delicately roll a suture into place rather than employing a much larger movement such as a wrist or elbow rotation. As a consequence, the Bender publication describes a largely unsatisfactory solution for two important reasons, first, Bender's protrusions are stamped or formed from sheet metal material in a manner that interrupts the integrity of the beam which further weakens the strength of the handle while gripping the needle. And second, the humps or protrusions on Bender's handle are constructed using a design that places the edges of the protrusions parallel or co-axial with the longitudinal axis of the instrument. This feature runs counter to proper or best practice use of the instrument as the side edges of the protrusions have a tendency to snag the gloves of the clinician thereby inhibiting the rolling thumb and finger motion employed by the clinician during performance of a delicate procedure.
An important feature of surgical instruments made from flexibly resilient sheet metal is that they are both flexible and resilient in the sense that they resist permanent deformation much more readily than surgical instruments made from solid cast materials or surgical instruments machined from wire or bar stock. But the flexibility is also a limitation in some cases as sheet metal will yield more readily to bending moments depending upon the location of forces acting upon the structure.
Therefore, to overcome the limitations of the prior art, the primary object of the invention is to provide an improved handle design that can deliver the required compression forces where necessary—resisting deformation—and, at the same time, remain consonant with best practice use of an instrument which will allow a surgeon to maintain tactile sensitivity while keeping a firm and positive hold on an instrument that is gripped using only finger pressure.
Another object of the present invention, and, specifically an object of the inventive handle integrally formed into an embodiment as a needle holder, is the design of an instrument capable of gripping needles of different diameters without permanent damage to the needle holder.